# Explaining The Straight Rod through Curved Hole Demo

In this video I'm calculating the exact curve the rod fits through in this demonstration, using simple trigonometry. When I first saw this demonstration I knew I had to figure what this curve is, and so I did, but it took me a lot of time and effort using linear algebra and vector analysis, which are usually taught in college. I wanted to find a simpler way using only high school level mathematics. It took me some time but I eventually found the two triangles I need to look at in order to calculate the curve with no fancy math.

Before even calculating the curve, I took the time and made a simple css animation of the spinning rod (no javascript ^_^).

The source code can be found here https://codepen.io/rad-head/pen/JvegVe

Feel free to modify and play with it.

For more information about building one (or even buying) visit the build article.